1. Field of the Invention
The present invention relates to an incinerator or cremation apparatus of the type which, apart from the combustion chamber proper, also has a secondary combustion chamber serviced by extra burner means for improved final combustion of the combustion gases.
2. Discussion of Prior Efforts in Field
A conventional incinerator included in a crematorium contains as a central part a combustion space for the coffin, heated with gas, oil or electricity, although most often by one or more oil burners. After the combustion space has been preheated to about 700.degree. C., heating is broken off and the coffin is inserted. Air is subsequently supplied, and the coffin ignites by itself and burns together with its contents. During the process the temperature rises to about 1100.degree. C. Excess secondary air is supplied to a post-combustion zone or chamber for final combustion of the combustion gases before they are led to a chimney. A modern variant of this incinerator type is described in SE-B-363 886, for example.
Such incinerators have several disadvantages, however, inter alia poor draught, largely due to the avoidance of large chimnies in crematoria for esthetic reasons. Since it is desired on ethical grounds to avoid actively supporting the combustion with an outside heat supply (e.g. oil burners), the result of combustion is often unsatisfactory due to the furnace temperature being too low at the beginning and end of the combustion process. This in turn leads to a fall in temperature in the post-combustion zone, causing incomplete final combustion with accompanying odour and smoke puffs through the chimney.
It has been attempted to put these disadvantages right in different developments of this conventional incinerator design. Accordingly, there are described, e.g. in U.S. Pat. No. 1,156,398, U.S. Pat. No. 3,538,864 and DE-C-257576 incinerators where a post-combustion chamber placed below the primary combustion chamber has been provided with a special afterburner, past which the combustion gases from the primary combustion chamber have to pass via one or more venting openings in the lower part of the primary chamber. There is indeed obtained improved chimney draught and better final combustion in these designs, but so the final combustion of the combustion gases will not be sufficiently effective for satisfactorily restricting or eliminating troublesome environmental poisons such as dioxines and nitrogen oxides. Due to the combustion gases being vented off in the lower part of the primary combustion chamber, there is also poor conversion of the combustion gases in the upper part of the combustion chamber, resulting in large fluctuations in composition of the combustion gases which come into the secondary combustion chamber and, as will be easily understood, this disadvantageously effects the final combustion. In addition, it is only in the design according to U.S. Pat. No. 3,538,864 that the heat in the post-combustion chamber is recovered to some extent for utilization in the primary combustion space.